US 5407982 A
It is herein disclosed a process for stabilizing freshly prepared polyketone polymer comprising contacting the polymer with a sufficient quantity of a stabilizing agent such as an alkali metal iodide salt or an onium iodide salt of nitrogen, phosphorus, or arsenic in which the organic groups comprising the cation coordination sphere is shielded by aromatic substituents. The inventive process results in stabilized polyketone polymers having and exhibiting improved thermal oxidative stability properties. It is also disclosed a stabilized polymer composition comprising a major amount of a polyketone polymer and a minor amount of an onium iodide salt of nitrogen, phosphorus, arsenic or combination thereof in which the cation coordination sphere is shielded by aromatic substituents.
1. A stabilized polymer blend comprising a major amount of linear polyketone polymer which is a linear alternating polymer of carbon monoxide and at least one ethylenically unsaturated hydrocarbon and a minor amount of an onium iodide salt of nitrogen, phosphorus, arsenic or combination thereof, in which the organic groups comprising the cation coordination sphere is shielded by aromatic substituents.
2. A blend as in claim 1 wherein said iodide salt is tetraphenylphosphonium iodide.
3. A blend as in claim 1 wherein said iodide salt is 5-methyl-3-(methylthio)-1,4-diphenyl-1-H-1,2,4-triazolium iodide.
4. A blend as in claim 1 wherein said iodide salt is an iodide salt of bis(triphenylphosphoranylidene)ammonium.
5. A blend as in claim 1 wherein said iodide salt is an insitu species of 4-iodophenyltriphenylphosphonium or 1,4-bis(triphenylphosphonium)benzene.
6. A blend as in claim 1 wherein said iodide salt is present in an amount of from 0.01 to 10 wt %.
7. A blend as in claim 1 further comprising a hindered phenol.
8. A blend as in claim 7 wherein said hindered phenol is octadecyl 3,5-di-tert. butyl-4-hydroxyhydrocinnamate.
9. A blend as in claim 7 wherein said hindered phenol is ethylene bis (oxyethylene) bis-(3-tert-butyl-4-hydroxy-5-methylhydrocinnamate).
10. A process for producing a stabilized linear polyketone polymer which is a linear alternating polymer of carbon monoxide and at least one ethylenically unsaturated hydrocarbon comprising contacting said polymer with an onium iodide salt of nitrogen, phosphorus, arsenic or combination thereof, in which the cation coordination sphere is shielded by aromatic substituents.
11. A process as in claim 10 wherein said contacting of said iodide salt is by means of melt compounding.
12. A process as in claim 10 wherein the contacting of the iodide salt with the polymer is by means of in-situ generation of said salt.
13. A process as in claim 10 wherein said iodide salt is present in an amount of from 0.1 to 1 wt %.
14. A process as in claim 10 further comprising the addition of a hindered phenol.
15. A process as in claim 11 wherein said iodide salt is an insitu species of 4-iodophenyltriphenylphosphonium or 1,4-bis(triphenylphosphonium)benzene.
16. A stabilized polymer blend which is a linear alternating polymer of carbon monoxide and at least one ethylenically unsaturated hydrocarbon comprising a major amount of a polyketone polymer and a minor amount of an alkali metal iodide salt.
17. A blend as in claim 16 wherein said alkali metal iodide salt is potassium iodide.
18. A blend as in claim 17 wherein said potassium iodide is present in an amount of from about 0.1 to 1 wt %.
19. A blend as in claim 18 further comprising a hindered phenol.
This invention generally relates to polyketone polymers. More particularly, this invention relates to stabilized polyketone polymers, and to a novel process for producing such stabilized polymers.
Polymers of carbon monoxide and olefins generally referred to as polyketones are well known in the art. Of particular interest among polyketone polymers, is the class of linear alternating polymers of carbon monoxide and at least one ethylenically unsaturated hydrocarbon. This class of polymers is disclosed in numerous U.S. patents assigned to Shell Oil Company, exemplified by U.S. Pat. No. 4,880,865 which is herein incorporated by reference.
Although the properties of polyketone polymers are suitable for many applications, linear alternating polymers of carbon monoxide and at least one ethylenically unsaturated hydrocarbon do exhibit a deterioration of physical properties upon thermal oxidative degradation. This degradation is due to a chemical attack of atmospheric oxygen on the polymer chains and is characteristic of most, if not all organic polymers. Oxidation is typically autocatalytic and occurs as a function of heat and oxygen, hence the term thermal oxidative degradation. It is desirable to inhibit the deterioration of polymer properties by stabilizing the polymer toward the adverse effects of heat and oxygen. There are a large number of thermal oxidative stabilizers which are employed commercially to stabilize thermoplastic polymers against such degradation. However, many of the thermal stabilizers which are known to be effective with polyolefins, polyamides, polyacetals, polyacrylates, etc. are only marginally or not at all effective when employed with polyketone polymers. It would therefore be of advantage to provide polyketone polymers which demonstrate improved heat stability to extend their use in higher temperature applications.
It is a general object of this invention to provide a stabilized polyketone polymer.
It is a further object of this invention to produce an oxidatively stable polyketone polymer.
It is also an object of this invention to provide a process for producing an oxidatively stabilized polyketone polymer.
Accordingly, it is now provided a method for producing an oxidatively stabilized polyketone polymer, comprising contacting freshly produced polyketone polymer with an onium iodide salt of a Group 15 element such as nitrogen, phosphorus, arsenic, or combination thereof in which the cation coordination sphere is shielded by aromatic substituents. It is also provided an oxidatively stabilized blend comprising a major amount of polyketone polymer and a minor amount of an onium iodide salt of a Group 15 element such as nitrogen, phosphorus, arsenic, or combination thereof in which the cation coordination sphere is shielded by aromatic substituents.
The method of contacting the polymer with the iodide salt includes diffusion, melt blending, or by in-situ formation of the iodide salt.
The materials useful in practicing this invention include a linear alternating polymer of carbon monoxide and at least one ethylenically unsaturated hydrocarbon (simply referred to as a polyketone polymer), an onium iodide salt of a Group 15 element of the Periodic Table of Elements such as nitrogen, phosphorus, arsenic, or combination thereof (henceforth sometimes referred to as iodide salt), and other common polymer additives. For instance, fillers, extenders, lubricants, pigments, plasticizers, and other polymeric materials can be added to the polyketone compositions being stabilized to improve or otherwise alter the properties of the compositions. In general, the practice of this invention involves suitably contacting sufficient quantities of the useful material to form a stabilized polyketone polymer composition.
The iodide salts (stabilizing agent(s)) of the present invention yield polyketone polymers with improved heat stability when the additive is adequately dispersed in the polymer matrix. Dispersion of the stabilizing agent(s)in the polymer can be accomplished by a variety of methods known to those skilled in the art. Such methods include a) melt compounding after contacting the stabilizing agent with polyketone polymer by powder mixing or solvent deposition, b) diffusion of the stabilizing agent into polymer articles using a solvent which has some miscibility with both polymer and the stabilizing agent, or c) in-situ generation of the stabilizing agent utilizing a polymer blend comprising of precursors which upon application of a sufficient amount of heat generates the stabilizing agent.
Thermal oxidative degradation of organic polymers relates to the deterioration of polymer properties due to the chemical reaction(s) between the polymer and atmospheric oxygen. While oxidation processes are complicated and mechanistic pathways of oxidation between different polymers may vary, oxidation is generally promoted by heat, often initiated by trace impurities such as metal ions or organic prodegradants, and characterized overall as autocatalytic in which carbon radicals and peroxyl radicals constitute key intermediates in the catalytic cycles. Consumption of oxygen by the polymer propagates the catalytic cycle and generates oxygenated species which either comprise part of the polymer or are evolved as gaseous products. These oxygenated species may further be prodegradative to the polymer. For example, hydroperoxides are not inherently stable and are capable of decomposing into new radicals, either thermally or catalyzed by trace impurities, which can then initiate additional oxidative cycles.
For polyketones it is believed that the thermal oxidative process involves the formation of oxygenates which under aging conditions cleave polymer chains and result in a reduction of molecular weight and a loss of polymer entanglement. Ultimately this results in a deterioration of polymer mechanical properties such as reduced impact strength, loss of elongation at break, and embrittlement. It would therefore be advantageous to stabilize the polyketone polymers towards these property losses either by reducing their overall rate of oxidation or reducing their rate of polymer chain scission.
This object is accomplished by adding through conventional methods such as melt blending, or non-conventional methods such as diffusion with a carrier such as water, or by in-situ formation of the stabilizing agent which is selected from the group consisting of onium iodide salts of a Group 15 element such as nitrogen, phosphorus, arsenic, or combination thereof in which the cation coordination sphere is shielded by aromatic substituents. The preferred such oniums are completely coordinated by an aryl substituent or are part of an aromatic ring. The useful iodide salts are exemplified by those listed in Table 1. Because not all iodide salts are useful in the practice of this invention, Table 1 also includes a list of some of the non-useful iodide salts. The contacting of the unstabilized polyketone polymer and the stabilizing agent in the manner previously disclosed results in a stabilized polymer.
TABLE 1__________________________________________________________________________Stabilizing Iodide Salts Non-stabilizing Iodide Salts__________________________________________________________________________Tetraphenylphosphonium PPh4 + ZnI2 - Zinc iodideBis(triphenylphosphoranylidene) Ph3 PN+PPh 3 CaI2 - calcium iodideammoniumInsitu 4-iodophenyltriphenyl- phosphonium 1,4-bis(triphenylphos- phonium)benzene ##STR1## Et4 NI - tetraethylammonium iodide Me4 NI - tetra- methylammonium idodide5-methyl-3-(methylthio-1,4-diphenyl 1H-1,2, 4-triazolium ##STR2## PPh3 MeI - Methyltriphenyl- phosphonium iodide9-phenanthryl triphenylphosphonium PMe (OPh)3 I - Methyltri- phenoxyphosphonium iodide PPh4 Cl - Tetraphenyl- phosphonium chlorideKI (diffusion only)1 PPh4 Br - Tetraphenyl- phosphonium__________________________________________________________________________ bromide 1 Other alkali metal iodide salts such as lithium, potassium, and sodium iodide are also within the scope of the invention.
The polymer of the invention, the inventive stabilizing agents, conventional additives typically useful in the formulation of the inventive composition, and a process for producing the stabilized polyketone polymer of the invention are discussed in more details in various sections of this specification.
The polyketone polymers which are employed as the major component of the oxidatively stabilized polymer composition of the invention are of a linear alternating structure and contain substantially one molecule of carbon monoxide for each molecule of ethylenically unsaturated hydrocarbon. The preferred polyketone polymers are copolymers of carbon monoxide and ethylene or terpolymers of carbon monoxide, ethylene and a second ethylenically unsaturated hydrocarbon of at least 3 carbon atoms, particularly an α-olefin such as propylene.
When the preferred polyketone terpolymers are employed as the major polymeric component of the blends of the invention, there will be within the terpolymer at least about 2 units incorporating a moiety of ethylene for each unit incorporating a moiety of the second hydrocarbon. Preferably, there will be from about 10 units to about 100 units incorporating a moiety of the second hydrocarbon. The polymer chain of the preferred polyketone polymers is therefore represented by the repeating formula ##STR3## where G is the moiety of ethylenically unsaturated hydrocarbon of at least 3 carbon atoms polymerized through the ethylenic unsaturation and the ratio of y:x is no more than about 0.5. When copolymers of carbon monoxide and ethylene are employed in the compositions of the invention, there will be no second hydrocarbon present and the copolymers are represented by the above formula wherein y is zero. When y is other than zero, i.e. terpolymers are employed, the --CO--CH2 --H2) units and the --CO--G-- units are found randomly throughout the polymer chain, and preferred ratios of y:x are from about 0.01 to about 0.1. The precise nature of the end groups does not appear to influence the properties of the polymer to any considerable extent so that the polymers are fairly represented by the formula for the polymer chains as depicted above.
Of particular interest are the polyketone polymers of number average molecular weight from about 1000 to about 200,000, particularly those of number average molecular weight from about 20,000 to about 90,000 as determined by gel permeation chromatography. The physical properties of the polymer will depend in part upon the molecular weight, whether the polymer is a copolymer or a terpolymer, and in the case of terpolymers the nature of the proportion of the second hydrocarbon present. Typical melting points for the polymers are from about 175° C. to about 300° C., more typically from about 210° C. to about 270° C. The polymers have a limiting viscosity number (LVN), measured in m-cresol at 60° C. in a standard capillary viscosity measuring device, from about 0.5 dl/g to about 10 dl/g, more frequently from about 0.8 dl/g to about 4 dl/g.
A preferred method for the production of the polyketone polymers is illustrated by U.S. Pat. No. 4,834,144 which is herein incorporated by reference.
Broadly speaking, the process of the invention involves dispersing a sufficient amount of stabilizing agent into polyketone polymer to improve the thermal oxidative stability of the polymer. In general, the stabilizers of this invention are employed in an amount within the range of from 0.01 to about 10 percent based on the weight of the polyketone polymer, preferably in the range of from 0.1 to 1.0 percent based on the weight of polyketone polymer. The stabilizer may be incorporated into the polyketone polymer at any stage of its processing, preferably prior to being subjected to elevated temperature, or at such times as desired to improve thermal oxidative stability. The method of incorporating the stabilizer is not considered to be critical so long as the method results in a substantially uniform blend of the composition components. Such methods include a) melt compounding after contacting the stabilizing agent with polyketone polymer by powder mixing or solvent deposition, b) diffusion of the stabilizing agent into polymer articles using a solvent which has some miscibility with both polymer and the stabilizing agent, or c) in-situ generation of the stabilizing agent utilizing a polymer blend comprising of precursors which upon sufficient amount of heat generates the stabilizing agent.
After preparation, the now stabilized polyketone polymers show improved retention of desired mechanical properties, such as resistance to embrittlement when tested under conditions of elevated temperature and air exposure. The test as disclosed in U.S. Pat. No. 4,994,511 subjects polymer samples to aerobic oven aging at various temperatures and monitors the time until brittle failure (cracking) occurs when sharply bent at an angle of 180°.
As will be seen from the examples and data table disclosed herein, freshly prepared polyketone polymers comprising the inventive stabilizing agent and prepared according to the methods of this invention have and exhibit improved stability, particularly improved thermal oxidative stability.
The following examples and tables further illustrate the various aspects of the invention.
Polymers used in the following examples are described in Table 2. An oven aging test was used throughout the examples to distinguish the performance of polymer additives. In this test, polymer sheet of 20 or 30 mil thicknesses was prepared either by melt extrusion or compression molding. Test specimens were then cut into 1 cm wide strips and placed into forced air circulating ovens at 100° C. or 125° C. Periodically, the strips were withdrawn from the oven and when cooled bent to a 180-degree angle. When the samples became sufficiently brittle to break under this test procedure it was considered to be a failure and the time to embrittlement was recorded.
TABLE 2______________________________________Polyketone polymers used in illustrative examples. LVN Tm BasePolymer dl/g °C. Form Additivesb______________________________________A 1.95 220 Ext. Sheeta 0.5% Irganox 1330 0.5% Nucrel 535B 1.86 220 Ext. Sheeta 0.2% Irganox 1330 0.2% CaHApc 0.3% Nucrel 535C 1.77 220 Powder 0.2% Irganox 1330 0.2% CaHAp 0.3% Nucrel 535D 1.73 220 Powder 0.2% Irganox 1330 0.2% CaHAp 0.3% Nucrel 535E 1.87 220 Powder None______________________________________ a Extruded sheet of 20 mil thickness. b Percent based on weight of polyketone polymer. c Calcium Hydroxyapatite. "IRGANOX 1330" (a trademark of CibaGeigy Corp.) is 1,3,5trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl) benzene, "NUCREL 535" (a trademark of DuPontMitsui Polychemicals, Ltd.) i Poly(ethyleneco-methacrylic acid) with 1.0% acrylic acid content
Examples 1-5 demonstrate the utility of iodide additives to heat aging when diffusionally incorporated into polyketone polymer. Test specimens were prepared by immersing polymer A in the form of 20 mil sheet into a water composition for 20-25 min at a temperature of 90°-95° C. The water used was HPLC grade, OmniSolv® supplied by EM Science. Water compositions used in examples 2-5 included: water alone, 0.30 wt % ZnI2, 2.0% KI, and saturated Ph4 PI which is only sparingly soluble in water at 90°-95° C. After exposure, the polymer specimens were cooled, wiped clean of any surface residue, and dried in a vacuum oven at 50° C. with a nitrogen purge over night. One centimeter wide oven test strips were then cut from the exposed sheets. For the sample which was exposed to Ph4 PI, neutron activation tests were conducted to determine the iodide present in the polymer after this exposure. Residual iodine measured ca. 900 ppm, calculating to 0.33% Ph4 PI present in this sample. Results of oven aging tests are shown in Table 3.
TABLE 3______________________________________Iodide additives diffusionally incorporated intopolyketone polymer. Days to FailureExample Exposure 125° C. 100° C.______________________________________1 -- 20 782 H2 O 22 813 H2 O/ZnI2 21 834 H2 O/KI 27 1215 H2 O/Ph4 PI 45 234______________________________________
Examples 2 and 3 show that simply exposing the polymer sheet to water alone or to a solution of ZnI2 does not result in improved heat stability. Exposure to KI and Ph4 PI results in an improvement in heat stability with Ph4 PI being far superior in its ability to stabilize this polyketone polymer--greater than 2 times the control, Example 1.
Test specimens used in Examples 6-10 were diffusionally prepared and then tested as described in Examples 2-5 using polymer A and water compositions which contained 2.0% of the corresponding test additive. The results are summarized in Table 4.
TABLE 4______________________________________Onium iodide salt additives diffusionally incorporatedinto polyketone polymer. Days to FailureExample Exposure 125° C. 100° C.______________________________________6 -- 24 1087 H2 O/Ph4 PBr 21 1138 H2 O/Ph4 PCl 25 1109 H2 O/Et4 NI 26 11710 H2 O/Ph4 PI 44 245______________________________________
Examples 7, 8, & 10 show that of the Ph4 P halide salts only the iodide is stabilizing to polyketone polymers. Example 9 demonstrates that alkyl ammonium iodides such as tetraethylammonium iodide (Et4 NI) are not effective in stabilizing polyketone polymers. This demonstrates that not all onium iodide salts are effective as stabilizers for polyketone polymer.
Examples 11-13 were prepared as described in Example 1-5 with the exception that extruded sheet of polymer B was used instead of polymer A. Test specimens for examples 12 & 13 were prepared similar to Examples 7-10. Oven aging results are shown in Table 5.
TABLE 5______________________________________Comparison of iodide salts diffusionally added topolyketone polymer. Days to FailureExample Exposure 125° C. 100° C.______________________________________11 -- 18 9712 H2 O/CaI2 19 9613 H2 O/Ph4 PI 28 128______________________________________
These examples show once again that not all iodide salts are stabilizing to polyketone polymer. Calcium iodide shows no improvement in time to embrittlement over the control.
Examples 14-16 demonstrate that powder mixing of Ph4 PI and polyketone polymer followed by melt processing results in a polymer composition with improved thermal oxidative stability. Examples 15 and 16 were prepared by combining 100 grams polymer C powder with Ph4 PI powder and then homogenizing by tumbling overnight. Each mixture was then extruded on a 15 mm Baker-Perkins twin screw extruder operating at a melt temperature of about 250° C. The extruded compositions were then used to make plaques of 30 mil thicknesses by compression molding. As shown in Table 6, compositions with Ph4 PI showed significantly improved time to embrittlement at 125° C. over the control.
TABLE 6______________________________________Aging performance of Ph4 PI melt blended into polyketonepolymer. Days to FailureExample Additive 125° C.______________________________________14 -- 815 0.25% Ph4 PI 1816 0.50% Ph4 PI 17______________________________________
Examples 17-32 compositions were prepared by melt processing as described in Examples 14-16 with the exception that polymer D was used instead of polymer C. Oven aging test results shown in Table 7, illustrate that onium iodide salts with alkyl substituents (ex. 18-22) exhibit no stabilizing influence on polyketone polymers. Examples 25 and 26 demonstrate the stabilizing influence of iodide salts other than Ph4 PI which also contain onium cations shielded by aromatic substituents, i.e. bis(triphenylphosphoranylidene)ammonium and a triazolium salt, respectively. In these examples, the increased stability was somewhat small, but similar in magnitude to the benefit from Ph4 PI in this polymer, Example 24.
TABLE 7______________________________________Aging performance of onium iodide salts melt blendedinto polyketone polymer. Days to FailureExample Additive 125° C. 100° C.______________________________________17 -- 17 7318 0.43% Ph3 MePI 16 4819 0.49% (PhO)3 MePI Not processable20 0.28% Et4 NI 12 3021 0.50% Et4 NI 12 3222 0.22% Me4 NI 11 3023 -- 2224 0.3% Ph4 PI 2625 0.43% PPNIa 2526 0.25% TIb 27______________________________________ a bis(triphenylphosphoranylidene)ammonium iodide b 5Methyl-3-(methylthio)-1,4-diphenyl-1H-1,2,4-triazolium iodide
Examples 27-39 compositions were prepared by melt processing as described in Examples 14-16 using the polymers and additives identified in Table 8. Example 30 demonstrates the improved resistance to embrittlement using only PPh4 I. Example 31 shows a significant improvement when a commercial hindered phenolic antioxidant such as Irganox 1076 is combined with Ph4 PI in polyketone polymers. This combination results in improved oven aging performance compared to using either individually. Examples 33-39 demonstrate that in-situ formation of phosphonium iodides from a phosphine and an organic iodide components improves the stability of polyketone polymer just as effectively as using Ph4 PI. Examples 34-37 shows that the use of either triphenyl phosphine or 1,4-diiodobenzene alone do not contribute to the stability of polyketone polymers. However, the combination of these additives in Example 33 yields a polymer with significantly improved heat aging performance. Examples 38 and 39, further show the beneficial effect when an organic iodide and triphenylphosphine are combined in the additive package.
TABLE 8______________________________________Aging performance of phosphonium iodides melt blendedinto polyketone polymers and generated in-situ. Days to FailureExample Polymer Additive 125° C.______________________________________27 E None 1528 E 0.5% Irganox 1076 1929 E 0.5% Irganox 245 2630 E 0.3% Ph4 PI 3831 E 0.5% Irganox 1076, 0.3% Ph4 PI 4332 E 0.5% Irganox 245, 0.3% Ph4 PI 3633 E 0.2% PPh3, 0.3% PhI2, 0.5% 42 Irganox 24534 E 0.3% PPI2, 0.5% Irganox 245 1135 D -- 1836 D 0.2% PPh3 1337 D 0.3% PPH3 1538 E 0.5% Irganox 245, 0.3% 9- 26 iodophenanthrene39 E 0.5% Irganox 245, 0.3% 9- 38 iodophenanthrene, 0.2% PPh3______________________________________ "IRGANOX 1076" (a trademark of CibaGeigy Corp.) is Octodecyl3,5-di-tert-butyl-4-hydroxyhydrocinnamate, "IRGANOX 245" (a trademark of CibaGeigy Corp.) is a Ethylenebis(oxyethylene)bis(3-tert-buthyl-4-hydroxy-5-methylhydrocinnamat
While this invention has been described in detail for the purpose of illustration, it is not to be construed as limited thereby but is intended to cover all changes and modifications within the spirit and scope thereof.